Lower right abdominal pain, small stools, gas

Hi about 4 months ago, I had two instances of bloody stool (cup full of blood - but none in last 4 months). Since then I have had on/off again dull lower right abdominal pain, with less occassional dull left lower abdominal pain. Also have had mixed stool results with normal / narrow / small and loose movements in this time. Have also noticed that one rib on both sides are slightly inflamed.

Sigmoidoscopy is negative, and blood tests are normal. Dont feel tired at all, and other than the dull pain, feel fine. Due for a colonoscopy soon, but needless to say, am worried!

Anyone have thoughts?